The present invention belongs to the fields of pharmacology and medicinal chemistry, and provides new pharmaceuticals which are useful for the treatment of diseases which are caused or affected by disorders of the serotonin-affected neurological systems, particularly those relating to the 1A receptor.
Pharmaceutical researchers have discovered in recent years that the neurons of the brain which contain monoamines are of extreme importance in a great many physiological processes which very strongly affect many psychological and personality-affecting processes as well. In particular, serotonin (5-hydroxytryptamine; 5-HT) has been found to be a key to a very large number of processes which affect both physiological and psychological functions. Drugs which influence the function of serotonin in the brain are accordingly of great importance and are now used for a surprisingly large number of different therapies.
The early generations of serotonin-affecting drugs tended to have a variety of different physiological functions, considered from both the mechanistic and therapeutic points of view. More recently, it has become possible to study the function of drugs at individual receptors in vitro or ex vivo, and it has also been realized that therapeutic agents with a single mechanism of action are often advantageous to the patient. Accordingly, the objective of research now is to discover not only agents which affect only functions of serotonin, but agents which affect only a single function of serotonin, at a single identifiable receptor.
The present invention provides compounds which have highly selective activity as antagonists of the serotonin 1A receptor.
The present invention provides a series of new aryl piperazine compounds, methods of using them for pharmaceutical purposes, and pharmaceutical compositions whereby the compounds may be conveniently administered.
The invention also provides methods of antagonizing, the 5HT-1A receptor, and therapeutic methods which are related to their effect on the 5HT-1A receptor. Such methods of treatment include, particularly, methods of alleviating the symptoms caused by withdrawal or partial withdrawal from the use of tobacco or of nicotine, comprising the administration to a patient in need of such treatment of a compound of Formula I 
wherein
Arxe2x80x2 is a mono- or bi-cyclic aryl or heteroaryl radical substituted with one to three substituents selected from the group consisting of hydrogen, (C1-C6)alkyl, (C1-C6)alkoxy, (C1-C6)alkylthio, (C2-C6)alkenyl, (C2-C6)alkynyl, (C1-C6)alkylhalo, (C3-C8)cycloalkyl, (C3-C8)cycloalkenyl or halo;
R1 is hydrogen, (C1-C6)alkyl, (C1-C6)alkoxy, (C1-C6)alkylthio;
R2 is phenyl, naphthyl or (C3-C12)cycloalkyl substituted with one or two substituents selected from the group consisting of hydrogen, (C1-C6)alkyl, (C1-C6)alkoxy, (C1-C6)alkylthio, (C2-C6)alkenyl, (C2-C6)alkynyl, (C1-C6)alkylhalo, (C3-C8)cycloalkyl, (C3-C8)cycloalkenyl or halo;
R3 is selected from the group consisting of hydrogen, (C1-C6)alkyl, (C1-C6)alkoxy, (C1-C6)alkylthio, (C2-C6)alkenyl, (C2-C6)alkynyl, (C1-C6)alkylhalo, (C3-C8)cycloalkyl, (C3-C8)cycloalkenyl or halo;
X is xe2x80x94C(xe2x95x90O)xe2x80x94, xe2x80x94CHOHxe2x80x94 or xe2x80x94CH2xe2x80x94;
or a pharmaceutically acceptable salt, racemate, optical isomer or solvate thereof.
Further, such therapeutic methods include methods of treatment of anxiety, depression, hypertension, cognitive disorders, psychosis, sleep disorders, gastric motility disorders, sexual dysfunction, brain trauma, memory loss, eating disorders and obesity, substance abuse, obsessive-compulsive disease, panic disorder and migraine.
A further treatment method provided by the present invention is a method for potentiating the action of a serotonin reuptake inhibitor, comprising administering to a patient an effective amount of a compound of Formula I in combination with the serotonin reuptake inhibitor.
More specifically, the present invention provides compounds of formula Ia; 
or the pharmaceutically acceptable salts thereof.
The compounds of formula Ia are enclosed within the scope of the compounds of Formula I and are therefore useful for the methods described herein for Formula I. For example, the present invention provides methods of antagonizing, the 5HT-1A receptor, and therapeutic methods which are related to their effect on the 5HT-1A receptor. Such methods of treatment include, particularly, methods of alleviating the symptoms caused by withdrawal or partial withdrawal from the use of tobacco or of nicotine, comprising the administration to a patient in need of such treatment, an effective amount of a compound of formula Ia. Further, such therapeutic methods include methods of treatment of anxiety, depression, hypertension, cognitive disorders, psychosis, sleep disorders, gastric motility disorders, sexual dysfunction, brain trauma, memory loss, eating disorders and obesity, substance abuse, obsessive-compulsive disease, panic disorder and migraine.
In addition, the present invention provides a method for potentiating the action of a serotonin reuptake inhibitor, comprising administering to a patient an effective amount of a compound of formula Ia in combination with the serotonin reuptake inhibitor.
The invention further provides a method of assisting a patient in ceasing or reducing their use of tobacco or nicotine comprising administering to a patient an effective amount of a compound of the Formula I or formula Ia.
This invention also encompasses novel processes for the synthesis of the compounds of formula I and formula Ia, the synthesis of novel intermediates thereof, and further encompasses novel intermediates per se.
In the present document, all descriptions of concentrations, amounts, ratios and the like will be expressed in weight units unless otherwise stated. All temperatures are in degrees Celsius.
The Compounds
It is believed that the general description of the compounds above is sufficient to explain their nature to the skilled reader; attention to the Examples which follow is also encouraged. Some additional description will be provided to assure that no misunderstanding occurs.
In the general description, the general chemical terms are all used in their normal and customary meanings. For example, the small alkyl and alkoxy groups, such as (C1-C6)alkyl and (C1-C6)alkoxy groups include, depending on the size of the groups, methyl, ethyl, propyl, isopropyl, n-butyl, s-butyl, pentyl, 3-methylbutyl, hexyl, and branched hexyl groups, and the corresponding alkoxy groups, as may be allowed by the individually named groups. Where a number of possible substituent groups are permitted on a group, such as the one to three alkyl, alkoxy or halo groups permitted on an Ar group, it will be understood by the reader that only substitution which is electronically and sterically feasible is intended.
The term xe2x80x9calkenylxe2x80x9d as used herein represents an unsaturated branched or linear group having at least one double bond. Examples of such groups include radicals such as vinyl, allyl, 2-butenyl, 3-butenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl, 2-hexenyl, 3-hexenyl, 4-hexenyl, 5-hexenyl as well as dienes and trienes of straight and branched chains.
The term xe2x80x9calkynylxe2x80x9d denotes such radicals as ethynyl, propynyl, butynyl, pentynyl, hexynyl as well as di- and tri-ynes.
The term xe2x80x9c(C1-C6)alkylthioxe2x80x9d defines a straight or branched alkyl chain having one to six carbon atoms attached to the remainder of the molecule by a sulfur atom. Typical (C1-C6)alkylthio groups include methylthio, ethylthio, propylthio, butylthio, pentylthio, hexylthio and the like.
The term xe2x80x9c(C1-C6)alkylhaloxe2x80x9d refers to alkyl substituents having one or more independently selected halo atoms attached at one or more available carbon atoms. These terms include chloromethyl, bromoethyl, trifluoroethyl, trifluoromethyl, 3-bromopropyl, 2-bromopropyl, 3-chlorobutyl, 2,3-dichlorobutyl, 3-chloro-2-bromo-butyl, trichloromethyl, dichloroethyl, 1,4-dichlorobutyl, 3-bromopentyl, 1,3-dichlorobutyl, 1,1-dichloropropyl, and the like. More preferred (C1-C6)alkylhalo groups are trichloromethyl, trichloroethyl, and trifluoromethyl. The most preferred (C1-C6)alkylhalo is trifluoromethyl.
The term xe2x80x9c(C3-C8)cycloalkylxe2x80x9d includes groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl. The term xe2x80x9c(C3-C8)cycloalkylxe2x80x9d includes (C3-C6)cycloalkyl.
The term xe2x80x9c(C3-C8)cycloalkenylxe2x80x9d represents an olefinically unsaturated ring having 3 to 8 carbon atoms including groups such as cyclopropenyl, cyclobutenyl, cyclopentenyl, cyclohexenyl, cycloheptenyl, cyclooctenyl, and the like. The term xe2x80x9c(C3-C8)cycloalkenylxe2x80x9d includes (C3-C6)cycloalkenyl.
The term xe2x80x9carylxe2x80x9d represents phenyl or naphthyl.
The term xe2x80x9cbicyclicxe2x80x9d represents either an unsaturated or saturated stable 7- to 12-membered bridged or fused bicyclic carbon ring. The bicyclic ring may be attached at any carbon atom which affords a stable structure. The term includes, but is not limited to, naphthyl, dicyclohexyl, dicyclohexenyl, and the like.
The term, xe2x80x9cmono or bicyclic heteroaryl radicalxe2x80x9d, refers to radicals derived from monocyclic or polycyclic, aromatic nuclei having 5 to 14 ring atoms and containing from 1 to 3 hetero atoms selected from the group consisting of nitrogen, oxygen or sulfur. Typical heterocyclic radicals are pyrrolyl, furanyl, thiophenyl, pyrazolyl, imidazolyl, indolizinyl, isoquinolyl, benzothienyl, isoindolizinyl, oxazolyl, indolyl, carbazolyl, norharmanyl, azaindolyl, dibenzofuranyl, thianaphthenyl, dibenzothiophenyl, indazolyl, imidazo(1.2-A)pyridinyl, anthranilyl, purinyl, pyridinyl, phenylpyridinyl, pyrimidinyl, pyrazinyl, quinolinyl.
The terms xe2x80x9chaloxe2x80x9d or xe2x80x9chalidexe2x80x9d are used in the above formula to refer to fluoro, chloro, bromo or iodo.
The term xe2x80x9caprotic solventxe2x80x9d refers to polar solvents of moderately high dielectric constant which do not contain an acidic hydrogen. Examples of common aprotic solvents are dimethylsulfoxide (DMSO), dimethylformamide, sulfolane, tetrahydrofuran, diethyl ether, methyl-t-butyl ether, or 1,2-dimethoxyethane.
The term xe2x80x9cprotic solventxe2x80x9d refers to a solvent containing hydrogen that is attached to oxygen, and hence is appreciably acidic. Common protic solvents include such solvents as water, methanol, ethanol, 2-propanol, and 1-butanol.
The term xe2x80x9cinert atmospherexe2x80x9d refers to reaction conditions in which the mixture is covered with a layer of inert gas such as nitrogen or argon.
As used herein, the term xe2x80x9cMexe2x80x9d refers to a xe2x80x94CH3 group, the term xe2x80x9cEtxe2x80x9d refers to a xe2x80x94CH2CH3 group and the term xe2x80x9cPrxe2x80x9d refers to a xe2x80x94CH2CH2CH3 group.
As used herein, the term xe2x80x9cstereoisomerxe2x80x9d refers to a compound made up of the same atoms bonded by the same bonds but having different three-dimensional structures which are not interchangeable. The three-dimensional structures are called configurations. As used herein, the term xe2x80x9cenantiomerxe2x80x9d refers to two stereoisomers whose molecules are nonsuperimposable mirror images of one another. As used herein, the term xe2x80x9coptical isomerxe2x80x9d is equivalent to the term xe2x80x9cenantiomerxe2x80x9d. The terms xe2x80x9cracematexe2x80x9d, xe2x80x9cracemic mixturexe2x80x9d or xe2x80x9cracemic modificationxe2x80x9d refer to a mixture of equal parts of enantiomers. The term xe2x80x9cchiral centerxe2x80x9d refers to a carbon atom to which four different groups are attached.
The term xe2x80x9cenantiomeric enrichmentxe2x80x9d as used herein refers to the increase in the amount of one enantiomer as compared to the other. A convenient method of expressing the enantiomeric enrichment achieved is the concept of enantiomeric excess, or xe2x80x9ceexe2x80x9d, which is found using the following equation:   ee  =                              E          1                -                  E          2                                      E          1                +                  E          2                      xc3x97    100  
wherein E1 is the amount of the first enantiomer and E2 is the amount of the second enantiomer. Thus, if the initial ratio of the two enantiomers is 50:50, such as is present in a racemic mixture, and an enantiomeric enrichment sufficient to produce a final ratio of 50:30 is achieved, the ee with respect to the first enantiomer is 25%. However, if the final ratio is 90:10, the ee with respect to the first enantiomer is 80%. An ee of greater than 90% is preferred, an ee of greater than 95% is most preferred and an ee of greater than 99% is most especially preferred. Enantiomeric enrichment is readily determined by one of ordinary skill in the art using standard techniques and procedures, such as gas or high performance liquid chromatography with a chiral column. Choice of the appropriate chiral column, eluent and conditions necessary to effect separation of the enantiomeric pair is well within the knowledge of one of ordinary skill in the art. In addition, the enantiomers of compounds of formulas I or Ia can be resolved by one of ordinary skill in the art using standard techniques well known in the art, such as those described by J. Jacques, et al., xe2x80x9cEnantiomers, Racemates, and Resolutionsxe2x80x9d, John Wiley and Sons, Inc., 1981. Examples of resolutions include recrystallization techniques or chiral chromatography.
The compounds of Formula I and formula Ia, as a class are highly active, important and particularly useful in the treatment methods of the present invention, but certain classes of the compounds are preferred. The following paragraphs describe such preferred classes. It will be understood that the preferred classes are applicable both to the treatment methods and to the new compounds of the present invention.
The reader will understand that the preferred classes of compounds may be combined to form additional, broader or narrower classes of preferred compounds.
a) Arxe2x80x2 is phenyl or pyridyl;
b) Arxe2x80x2 is naphthyl;
c) Arxe2x80x2 is pyrazinyl, pyrimidinyl, pyrrolyl, furyl, thienyl, indolyl, purinyl, imidazolyl, pyrazolyl, indolizinyl, benzofuranyl, isoquinolyl, quinolyl, benzothienyl or isoindolizinyl;
d) Arxe2x80x2 is optionally substituted with (C1-C6)alkyl, (C1-C6)alkoxy, halo, (C2-C6)alkenyl or (C2-C6)alkynyl;
e) Arxe2x80x2 is optionally substituted with (C1-C4)alkyl, (C1-C4)alkoxy or halo;
f) R1 is hydrogen;
g) R1 is (C1-C6)alkyl or (C1-C6)alkoxy;
h) R1 is (C1-C2)alkyl or (C1-C2)alkoxy;
i) R2 is phenyl;
j) R2 is (C3-C8)cycloalkyl;
k) R2 is (C3-C6)cycloalkyl;
l) R2 is cyclohexyl;
m) R3 is (C1-C6)alkyl, (C1-C6)alkoxy or halo;
n) R3 is (C1-C4)alkyl, (C1-C4)alkoxy or halo;
o) X is xe2x80x94Cxe2x95x90O;
p) X is xe2x80x94CHOH; and
q) X is xe2x80x94CH2.
r) formula Ia
s) the enantiomer of formula Ia wherein the [xcex1]D20 in methanol is (+).
Since the compounds of this invention are basic in nature, they accordingly react with any of a number of inorganic and organic acids to form pharmaceutically acceptable acid addition salts. Included within the scope of the invention are the mono- and di-salts. Acids commonly employed to form such salts are inorganic acids such as hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuric acid, phosphoric acid, and the like, and organic acids, such as p-toluenesulfonic acid, methanesulfonic acid, oxalic acid, p-bromophenylsulfonic acid, carbonic acid, succinic acid, citric acid, benzoic acid, acetic acid and the like. Examples of such pharmaceutically acceptable salts thus are the sulfate, pyrosulfate, bisulfate, sulfite, bisulfite, phosphate, monohydrogenphosphate, dihydrogenphosphate, metaphosphate, pyrophosphate, chloride, bromide, iodide, acetate, propionate, decanoate, caprylate, acrylate, formate, isobutyrate, caproate, heptanoate, propiolate, oxalate, malonate, succinate, suberate, sebacate, fumarate, maleate, butyne-1,4-dioate, hexyne-1,6-dioate, benzoate, chlorobenzoate, methylbenzoate, dinitrobenzoate, hydroxybenzoate, methoxybenzoate, phthalate, sulfonate, xylenesulfonate, phenylacetate, phenylpropionate, phenylbutyrate, citrate, lactate, xcex2-hydroxybutyrate, glycollate, tartrate, methanesulfonate, propanesulfonate, naphthalene-1-sulfonate, naphthalene-2-sulfonate, mandelate and the like. Preferred pharmaceutically acceptable salts are the monohydrochloride, dihydrochloride, monohydrobromide, dihydrobromide, Formula I/succinate(1:1), formula Ia/succinate(1:1), Formula I/succinate 2:1, formula Ia/succinate 2:1, phosphate, d-tartrate, l-tartrate or maleate. It is understood by one of ordinary skill that hydrates of the free base or of the pharmaceutically acceptable salts are included within the scope of the present invention.
Many of the compounds of Formula I, including formula Ia, are optical isomers. For example, the compounds have an asymmetric center (or chiral center) at the carbon atom to which R1 and X are attached. However, when a compound of the present invention is named without an indication of asymmetric form, any and all of the possible asymmetric forms are intended. This invention is not limited to any particular isomer but includes all possible individual isomers and racemates.
The intermediates and final products may be isolated and purified by conventional techniques, such as, purification with chromatography using silica gel or recrystallization of crystalline isolates.
It will be readily appreciated by the skilled artisan that the starting materials which are not described are either commercially available or can be readily prepared by known techniques from commercially available starting materials. All other reactants used to prepare the compounds in the instant invention are commercially available.
The compounds of the invention are generally prepared according to the following schemes. 
Starting material (1) is treated with a base, preferably potassium tert-butoxide, followed by alkylation with 2-bromomethyl-1,3-dioxolane. Other appropriate bases include sodium hydride, sodium hydroxide, potassium hydroxide, potassium carbonate, cesium carbonate and the like.
The reaction is preferably conducted in a solvent such as dimethyl sulfoxide at a temperature of 15xc2x0 C. to reflux, with a temperature of 45-55xc2x0 C. being most preferred, and is substantially complete in 1 to 24 hours to prepare intermediate (2).
Treatment of (2) with an acid, such as hydrochloric acid or p-toluene-sulfonic acid in a suitable organic solvent, achieves aldehyde (3). Generally, the reaction is conducted in a protic solvent, such a mixture of aqueous acid and acetone, at temperatures of from about 5xc2x0 to 75xc2x0 C., preferably at ambient temperature.
Aldehyde (3) is coupled with the desired aryl piperidine (4) by reductive amination to prepare (5). The reaction is preferably conducted at ambient temperature in a non-reactive solvent such as dichloroethane or methylene chloride in the presence of sodium triacetoxyborohydride and is substantially complete in one to 24 hours. See for example A. F. Abdel-Magid, et al., J. Org. Chem., 61, 3849 (1996).
Reduction of (5) is readily accomplished using a reducing agent such as sodium borohydride or, preferably, diisobutylaluminum hydride to prepare the hydroxy compound (6). The reaction is preferably conducted in an organic solvent such as methylene chloride at temperatures of from about xe2x88x9220xc2x0 C. to 0xc2x0 C.
Further reduction of (6) to achieve product (7) may be achieved by treatment with a reducing agent such as triethylsilane or boron trifluoride (when R2 is phenyl or substituted phenyl) or by treatment with an acid, such as hydrochloric acid or trifluoroacetic acid, in an aprotic solvent such as tetrahydrofuran, at ambient temperature to form the double bond, followed by hydrogenation with, for example, hydrogen and palladium on carbon.
Starting material (1) is either commercially available or can be prepared by coupling (8) [See Nahm and Weinreb, Tetrahedron Lett., 22, 3815, (1981)] and (9) as described in Scheme II, below. 
M is a metallic salt, such as lithium or magnesium halide. The reaction is preferably conducted under an inert atmosphere preferably nitrogen, in an aprotic solvent, such as tetrahydrofuran, at ambient temperatures.
More specifically, the compounds of formula Ia can be prepared following the procedure described in Scheme III. All substituents, unless otherwise indicated, are previously defined. The reagents and starting materials are readily available to one of ordinary skill in the art. 
In Scheme III, step A, the ester of structure (10) is treated with benzylmagnesium chloride or benzylmagnesium bromide under standard conditions well known in the art to provide the ketone of structure (11). For example, about 1.05 to about 1.1 equivalents of a suitable amine, such as dimethylamine is dissolved in a suitable organic solvent, such as tetrahydrofuran (cooled to about xe2x88x925xc2x0 C.) under an inert atmosphere. The solution is warmed to room temperature and 1.0 equivalents of the ester (10) are added with stirring. Then approximately 1.0 to 1.05 equivalents of benzylmagnesium chloride is slowly added to the solution, maintaining the temperature at about 15-20xc2x0 C. with a cooling bath during the addition. After addition is complete, the reaction is stirred at room temperature for about 1 to 2 hours, then cooled to less than 0xc2x0 C. and then carefully quenched with a suitable acid, such as HCl. The quenched reaction is then extracted with a suitable organic solvent, such as tert-butyl methyl ether (hereinafter referred to as MTBE), the organic layers are-combined, dried over anhydrous magnesium sulfate, filtered and concentrated to provide ketone (11). Ketone (11) can be purified by techniques well known in the art, such as flash chromatography on silica gel with a suitable eluent, such as ethyl acetate/hexane to provide the purified material. Alternatively, the crude ketone (11) can be carried on to step B.
In Scheme III, step B, ketone (11) is alkylated with bromoacetaldehyde diethyl acetal, and then iodomethane, under conditions well known in the art to provide compound of structure (12). For example, ketone (11) is dissolved in a suitable organic solvent, such as methyl sulfoxide and treated with about 1.05 to about 1.1 equivalents of a suitable base, such as potassium tert-butoxide. The reaction is stirred for about 15 to 30 minutes and about 1.0 to about 1.05 equivalents of bromoacetaldehyde diethyl acetal is added dropwise to the reaction. One of ordinary skill in the art would readily appreciate that bromoacetaldehyde dimethyl acetal, bromoacetaldehyde ethylene acetal and the like may be used in place of the corresponding diethyl acetal. The reaction mixture is then heated to about 50xc2x0 C. for about 2 to 2.5 hours. The reaction mixture is then cooled with an ice/water bath and about 2.2 equivalents of a suitable base, such as potassium tert-butoxide is added. The reaction is allowed to stir for about 15 to 30 minutes with continued cooling and then about 1.5 to about 1.8 equivalents of iodomethane is added dropwise to the reaction mixture keeping the temperature of the mixture below 41xc2x0 C, preferably below 21xc2x0 C. After addition is complete, the reaction is warmed to room temperature and stirred for about 1 to 4 hours. The reaction mixture is then partitioned between water and a suitable organic solvent, such as MTBE. The layers are separated and the organic phase is washed with water, brine, dried over anhydrous magnesium sulfate, filtered and concentrated under vacuum to provide the compound (12).
In Scheme III, step C, compound (12) is hydrolyzed under acidic conditions to provide aldehyde (13) in a manner analogous to the procedure described in Scheme I. More specifically, for example, compound (12) is dissolved in a suitable organic solvent, such as acetone and treated with a suitable acid, such as hydrochloric acid. The reaction mixture is stirred for about 1 to 3 hours at room temperature. The reaction mixture is then extracted with a suitable organic solvent, such as ethyl acetate or methylene chloride, the organic extracts are combined, washed with brine, dried over anhydrous magnesium sulfate, filtered and concentrated under vacuum to provide aldehyde (13). Aldehyde (13) can be purified by techniques well known in the art, such as flash chromatography on silica gel with a suitable eluent, such as ethyl acetate/hexane. Alternatively, crude aldehyde (13) can be used directly in step D.
In Scheme III, step D, aldehyde (13) is reductively aminated, under conditions well known in the art, with piperazine (14) to provide the compound of formula Ia in a manner analogous to the procedure described in Scheme I. More specifically, for example, aldehyde (13) is dissolved in a suitable organic solvent, such as methylene chloride. To this solution is added about 1.1 equivalents of piperazine (14). Acetic acid may optionally be added to aid in dissolution of the piperazine (14). Then about 1.2 to 1.3 equivalents of sodium triacetoxyborohydride is added and the reaction is stirred at room temperature for about 3 to 5 hours. The reaction is then quenched by addition of a suitable base, such as aqueous sodium hydroxide to provide a pH of about 10 to about 12. The quenched reaction is then extracted with a suitable organic solvent, such as methylene chloride. The organic extracts are combined, washed with brine, dried over anhydrous magnesium sulfate, filtered and concentrated under vacuum to provide the compound of formula Ia. This material can then be purified by techniques well known in the art, such as flash chromatography on silica gel with a suitable eluent, such as ethyl acetate/hexane.
The free base of formula Ia can be converted to the corresponding pharmaceutically acceptable salts under standard conditions well known in the art. For example, the free base of formula Ia is dissolved in a suitable organic solvent, such as methanol, treated with one equivalent of maleic or oxalic acid for example, or two equivalents of hydrochloric acid for example, and then concentrated under vacuum to provide the corresponding pharmaceutically acceptable salt. The residue can then be purified by recrystallization from a suitable organic solvent or organic solvent mixture, such as methanol/diethyl ether.
In Scheme III, step E, the (+) enantiomer of formula Ia can be separated from the (xe2x88x92) enantiomer using techniques and procedures well known in the art, such as that described by J. Jacques, et al., xe2x80x9cEnantiomers, Racemates, and Resolutionsxe2x80x9d, John Wiley and Sons, Inc., 1981. For example, chiral chromatography with a suitable organic solvent, such as ethanol/acetonitrile and Chiralpak AD packing, 20 micron can also be utilized to effect separation of the enantiomers.
In Scheme III, step F, the (+) enantiomer of formula Ia is converted to its pharmaceutically acceptable salt, such as the monohydrochloride, dihydrochloride, monohydrobromide, dihydrobromide, formula Ia/succinate(1:1), formula Ia/succinate 2:1, phosphate, d-tartrate, l-tartrate or maleate salt, in a manner analogous to the procedure described at the end of step D above.
Alternatively, compounds of structure (5) can be prepared following the procedure described in Scheme IV. All substituents, unless otherwise indicated, are previously defined. The reagents and starting materials are readily available to one of ordinary skill in the art. 
In Scheme IV, step A, aldehyde (15) is combined with a suitable organometallic reagent (16) under conditions well known in the art to provide alcohol (17). Examples of suitable organometallic reagents include Grignard Reagents, alkyl lithium reagents, alkyl zinc reagents, and the like. Grignard Reagents are preferred. For examples of typical Grignard Reagents and reaction conditions, see J. March, xe2x80x9cAdvanced Organic Chemistry: Reactions, Mechanisms, and Structurexe2x80x9d, 2nd Edition, McGraw-Hill, pages 836-841 (1977). More specifically, aldehyde (15) is dissolved in a suitable organic solvent, such as tetrahydrofuran or toluene, cooled to about xe2x88x925xc2x0 C. and treated with about 1.1 to 1.2 equivalents of a Grignard reagent of formula (16) wherein M is MgCl or MgBr. The reaction is allowed to stir for about 0.5 to 2 hours, then quenched, and alcohol (17) is isolated. For example, the reaction mixture is poured onto ice-cold 1N HCl, the quenched mixture is extracted with a suitable organic solvent, such as toluene, the organic extracts are dried either azeotropically or over a suitable drying agent, such as anhydrous magnesium sulfate, filtered and concentrated under vacuum to provide alcohol (17).
In Scheme IV, step B, alcohol (17) is oxidized under standard conditions well know in the art, such as those described by J. March, xe2x80x9cAdvanced Organic Chemistry: Reactions, Mechanisms, and Structurexe2x80x9d, 2nd Edition, McGraw-Hill, pages 1082-1084 (1977), to provide ketone (1). [Ketone (1) is the starting material used in Scheme I above.]
For example, alcohol (17) is dissolved in a suitable organic solvent, such as methylene chloride, the solution cooled with a wet ice-acetone bath, and treated with 2.5 to 3.0 equivalents of dimethyl sulfoxide. After stirring for about 30 minutes, the reaction is then treated with about 1.8 equivalents of P2O5. The reaction is allowed to stir for about 3 hours and then, preferably, treated over about 30 minutes with about 3.5 equivalents of a suitable amine, such as triethylamine. The cooling bath is then removed and the reaction is allowed to stir for about 8 to 16 hours. The ketone (1) is then isolated by standard extraction techniques well known in the art. The above oxidation is also performed using standard Swern Oxidation conditions which are well known to one of ordinary skill in the art.
In Scheme IV, step C, ketone (1) is treated with a suitable base followed by addition of the alkene (18), wherein X is a suitable leaving group, to provide compound (19). For example, ketone (1) is combined with an excess of alkene (18) in a suitable organic solvent, such as tetrahydrofuran, and cooled with a wet ice acetone bath. Examples of suitable leaving groups are Cl, Br, I, tosylate, mesylate, and the like. Preferred leaving groups are Cl and Br. About 1.1 equivalents of a suitable base is added and the reaction is allowed to stir for about 2 hours at room temperature. Examples of suitable bases are potassium tert-butoxide, sodium hydride, NaN(Si(CH3)3)2, LDA, KN(Si(CH3)3)2, NaNH2, sodium ethoxide, sodium methoxide and the like. Potassium tert-butoxide is the preferred suitable base. The reaction is then quenched with aqueous acid and compound (19) is isolated by extraction with a suitable organic solvent, such as heptane. The heptane extracts are washed with sodium bicarbonate, dried over anhydrous magnesium sulfate, filtered and concentrated under vacuum to provide compound (19).
In Scheme IV, step D, compound (19) is treated with a suitable oxidizing agent to provide aldehyde (3). [Aldehyde (3) is also prepared in Scheme I.] Examples of suitable oxidizing agents are ozone, NaIO4/Osmium catalyst, and the like. Ozone is the preferred oxidizing agent. Examples of suitable oxidizing reagents and conditions are described by J. March, xe2x80x9cAdvanced Organic Chemistry: Reactions, Mechanisms, and Structurexe2x80x9d, 2nd Edition, McGraw-Hill, pages 1090-1096 (1977).
For example, compound (19) is dissolved in a suitable organic solvent, such as methanol, a small amount of Sudan III is added, and the solution is cooled to about xe2x88x9220xc2x0 C. Ozone is bubbled into the solution for about 4 hours until the pink color turns to a pale yellow color. Then Me2S is added to the reaction mixture and the cooling bath is removed. Concentration of the reaction mixture under vacuum provides the intermediate dimethyl acetal of aldehyde (3). This dimethyl acetal is readily hydrolyzed under standard acidic conditions to provide aldehyde (3). Alternatively, direct acidic work-up of the crude reaction mixture provides aldehyde (3). Alternatively, aldehyde (3) can be obtained directly by ozonolysis of (19) in a non-acetal forming solvent, such as methylene chloride.
In Scheme IV, step E, aldehyde (3) is reductively aminated under conditions analogous to those described above in Scheme III, step D, to provide compound (5). [Compound 5 is also prepared in Scheme I.]
Scheme V provides an alternative synthesis for the preparation of compound (5). All substituents, unless otherwise indicated, are previously defined. The reagents and starting materials are readily available to one of ordinary skill in the art. 
In Scheme V, step A, aldehyde (3) is condensed with piperidine (4) under standard conditions well known in the art to provide the enamine (20). For example, about 1.05 equivalents of aldehyde (3) dissolved in a suitable organic solvent, such as isopropyl acetate or isopropanol, is added to neat piperazine (4), free base. Additional organic solvent is added to produce a slurry and the reaction is stirred for about 1 to 2 hours. The enamine (20) is then isolated by standard techniques, such as collection by filtration.
In Scheme V, step B, the enamine (20) is hydrogenated under conditions well known by one of ordinary skill in the art to provide compound (5). For example, enamine (20) is combined with a suitable organic solvent, such as isopropyl alcohol and a catalytic amount of 5% palladium on carbon in a Parr bottle. The mixture is placed under 50 psi of hydrogen and shaken for about 2 days at room temperature. The slurry is then filtered to remove catalyst and the filtrate is concentrated to provide compound (5).
The following examples represent typical syntheses of the compounds of Formula I and formula Ia as described generally above. These examples are illustrative only and are not intended to limit the invention in any way. The reagents and starting materials are readily available to one of ordinary skill in the art. As used herein, the following terms have the meanings indicated: xe2x80x9caqxe2x80x9d refers to aqueous; xe2x80x9ceqxe2x80x9d refers to equivalents; xe2x80x9cgxe2x80x9d refers to grams; xe2x80x9cmgxe2x80x9d refers to milligrams; xe2x80x9cLxe2x80x9d refers to liters; xe2x80x9cmLxe2x80x9d refers to milliliters; xe2x80x9cxcexcLxe2x80x9d refers to microliters; xe2x80x9cmolxe2x80x9d refers to moles; xe2x80x9cmmolxe2x80x9d refers to millimoles; xe2x80x9cpsixe2x80x9d refers to pounds per square inch; xe2x80x9cminxe2x80x9d refers to minutes; xe2x80x9chxe2x80x9d refers to hours; xe2x80x9cxc2x0 C.xe2x80x9d refers to degrees Celsius; xe2x80x9cTLCxe2x80x9d refers to thin layer chromatography; xe2x80x9cHPLCxe2x80x9d refers to high performance liquid chromatography; xe2x80x9cRfxe2x80x9d refers to retention factor; xe2x80x9cRtxe2x80x9d refers to retention time; xe2x80x9cxcex4xe2x80x9d refers to part per million down-field from tetramethylsilane; xe2x80x9cTHFxe2x80x9d refers to tetrahydrofuran; xe2x80x9cDMFxe2x80x9d refers to N,N-dimethylformamide; xe2x80x9cIPAxe2x80x9d refers to isopropyl alcohol; xe2x80x9ciPrOAcxe2x80x9d refers to isopropyl acetate; xe2x80x9cAcOHxe2x80x9d refers to acetic acid; xe2x80x9cHRMSxe2x80x9d refers to high resolution mass spectrometry; xe2x80x9cEt3Nxe2x80x9d refers to triethylamine; xe2x80x9cLDAxe2x80x9d refers to lithium diisopropyl amide; xe2x80x9cRTxe2x80x9d refers to room temperature; xe2x80x9cSRIxe2x80x9d refers to serotonin reuptake inhibitor; xe2x80x9caqxe2x80x9d refers to aqueous; and xe2x80x9cMTBExe2x80x9d refers to tert-butyl methyl ether.